At present, an explosive/drug detector employing ion mobility spectrometry has become a quick, sensitive and portable instrument for field detection. The instrument has already been widely applied by military and security inspection agencies to detect the presence of trace analytes such as explosives, narcotics and chemical warfare agents, etc.
When the ion mobility spectrometer is used to detect contraband compounds, in addition to a vapor sampling mode, particle sampling is the most commonly used sampling mode. By adopting the particle sample collection mode, a sampling substrate, e.g., a sampling swab, is first used to wipe the surface of an object to collect particulates of explosives or drugs, and then the swab is inserted into the sample inlet port of the instrument for detection and identification.
Currently, particle sampling for the ion mobility spectrometer is conducted in two modes:
1. Direct Wiping
When using this mode, an operator wearing gloves holds a strip-like sampling swab as disclosed in the U.S. Pat. No. 5,476,794A or a specially shaped sampling substrate or carrier to directly wipe an article surface for sample collection. The U.S. Pat. No. 5,571,976 discloses a sample collection method using a carrier with the configuration of a small bag which can be mounted on the user's fingers. The sample carrier comprises top and bottom layers of a cotton mesh material, which are secured together along three sides, i.e., two side edges and a rear edge, and open end along a fourth side, i.e., a front edge, to enable the user's fingers to be inserted with the opening being sized to receive two fingers. Mounted on an operator's fingers, the device is run over surfaces to be tested for sample collection. It is then placed in a frame holder and inserted into an inlet port of an analysis device for analysis. To prevent the hand from contacting the surfaces of interest (the contaminated hand will interfere with the subsequent sampling and detection) or to allow for a width to accommodate the fingers, the sampling swab has to be made relatively large and correspondingly the sample feeding inlet port of the instrument is also made very large. This will not only cause great waste of sampling wipes, and, more importantly, such a very large sample inlet port has a lot of drawbacks: firstly, uncentralized heat and the resultant low heating efficiency adversely affect the sensitivity of the instrument; secondly, a large electrical power consumption shortens the working time of the battery so that the battery needs to be replaced frequently, thus affecting the application performance of the instrument.
2. Wiping Using a Sampling Device
In the mode of using a sampling device to hold a swab for swiping sampling, as disclosed in the U.S. Pat. No. 5,859,375A and the PCT patent WO2007069088A3, the hand-held sampling apparatus has a handle, a sampling head connected to the handle and a mechanism for retaining the sampling swab on the sampling head. The sampling swab is preferably a sheet-form flexible material which is mounted so as to present a collection portion thereof for sample collection. The apparatus enables quick and efficient sampling in an area to be tested, while keeping a user's hands away from the surface, and meanwhile facilitates sample collection from otherwise inaccessible areas. This imposes high requirements for the sampling apparatus. Particularly, sampling swabs are required to be flat and smooth, uncurled, unwrinkled, uncontaminated and simply operable during storage or while in use. To guarantee sampling swabs being flat and smooth, uncurled, unwrinkled and uncontaminated during storage, the sampling swabs employed by the prior art ion mobility spectrometer can only be prepared in individual pieces (single pieces). Accordingly, the swipe sampling apparatus can only be adapted for use of the individual sampling swabs, that is, for each detection a sampling swab must be taken out from a sampling swab storage container, then mounted and used for sample collection and detection. These steps not only make the sampling operations complex but, more importantly, are extremely liable to cause contamination of other unused sampling swabs which brings very serious problems for the storage of swabs.